1. Field of the Invention
This invention relates to plastic bags, and more particularly to an apparatus and method for forming flapless aperture cutouts in a pack of plastic bags and the pack of bags made by the apparatus and method.
2. Description of the Prior Art
Many groceries stores and other merchants use a style of plastic bag to bag groceries and other merchandise commonly referred to as T-shirt bags. T-shirt bags are pleated bags which are closed, by heat sealing, at a bottom edge, and have a pair of integral loop handles extending upwardly from side edges to define an open mouth of the bag therebetween. T-shirt bags are normally provided in packs of aligned bags and these packs of bags are typically used with bagging racks.
T-shirt bags are manufactured by the following process. A continuous tube of high density polyethylene ("HDPE") plastic, or other plastic materials having the desired color, thickness, and diameter (such as low or linear low density polyethylene ("LDPE" or "LLDPE") or any of the polyolefins) is formed on a extruding machine. The continuous plastic tube is then passed over rollers to roll the continuous plastic tube onto a spool. If the bags to be formed from the continuous tube of HDPE are to be printed on one or both sides, the newly formed continuous plastic tube will be subjected to corona surface treatment, wherein the side or sides of the continuous flattened tube of plastic to be later printed will be passed by high voltage corona discharge electrodes. Corona surface treatment affects electrical and chemical changes on the plastic's outer surface to prepare that surface of the bag for printing. Regardless of whether the bags will be printed on one or both sides, it is a common practice in the plastic bag manufacturing industry to corona surface treat the entire outer surface of the rolls of continuous plastic tubing so that printing can be done on either one or both either sides, as later may be required. Corona surface treatment also helps contribute to frangible bonding between adjacent surfaces of corona treated plastic sheet material when these surfaces are compressed together.
After being corona surface treated (if the bags might be printed), the roll of continuous plastic tube is pleated on a pleated machine. Following this, a bagging machine heat seams and cuts sections of the pleated tube at top and bottom edges to form closed and flattened pleated bags of a desired length and width, with the pleated sides being at both sides of the flattened pleated bags. These sections are often referred to as "pillowcases." Further downstream of the heat seaming and cutting step, the pillowcases are stacked in aligned stacks. Thereafter, hydraulic die cutting or other cutting methods are utilized to cut, compresses, serrate, and remove material at the stacked pillowcases' top portions to form the various cuts, areas of compression, serration, and the like, to form these features in the finished bags of the bag pack. For example, cutting removes material to form the shape of the handles and the outline of the mouth and mouth tab, and forms desired apertures through the handles and mouth tab. Blunt blades, cold or heat posts and pins, and other means can be used to frangibly or permanently hold together portions of the bag. These can be combined with cutting means to compress the bag material together, and to form apertures in the bag pack. The apertures in the handles and the apertures in the mouth tab are provided for use in supporting the pack of self-opening bags on hooks positioned on a bagging rack. Each loop handle will comprise four layers of plastic material since they are cut out from the pleated side portions of the bag. It is this portion of the method that is the focus of Applicants' invention.
The apertures in handles and central mouth tab can be relatively straight, curved, horseshoe shaped, hooked, J-shaped, or have other shapes. When a cut line consist of a shape other than a substantially straight line, and no two points of a cut line intersect, a flap is formed. These flaps can be variously used to allow a portion of a bag pack, for example such as a handle or mouth tab, to be mounted on a suspension arm or hook of a bagging rack. The stack of flaps will be pushed away to accept the suspension arm or hook, and can provide additional friction to retain a portion of the bag pack in place without sliding around. There are problems associated with having flaps, however. When a single bag is removed from the stack of bags on a bagging rack these flaps can flop around and appear unsightly. Another problem is that if these flaps are pulled or get caught on something, the cut line defining the flap can migrate from the terminal ends of the cut line, causing unintended tearing of the bag, and also possible separation of the flap from the bag. Straight or relatively straight cuts do not have the problem of flaps becoming separated, but straight cuts tend to propagate and can cause unintentional tearing. For this reason, sometimes tear guards are provided at or adjacent the terminal end of cut lines, which can consist of curved cut line. The alternative to providing either a slit bag design problem or forming openings in a stack of bags during the manufacturing relatively straight cut line or flaps, is to eliminate flaps entirely by forming cutout. These cutouts can be circular or have some other shape. However, forming cutouts though stacks of thin film material has been difficult from a manufacturing standpoint since these small cutout tend to become scattered and fly around the manufacturing facility and are difficult to collect.
Turning again to bag styles, there are at two major styles of central tab arrangements. In a one style, which will be termed a "tabbed" style, the central suspension tab provided above the mouth region of the bag between the arms has an aperture formed therethrough. This aperture is used to support the center of the bag pack on a hook of a bagging rack. A slit, tearing line, or perforation, or some combination of these, is located below the suspension tab. In front-side free bag styles, the slit extends entirely across the front wall of the bag, but some material remains on the rear wall of material to hold the tab to the bag and therefore support the bag pack. In the more typical tabbed style, the front side of the bag is not cut all the way through. In tabbed bag packs, the stack of suspension tabs are generally fixed together, such as with a heat weld, to form a "book". When a single bag is pulled forward from the bagging rack to remove it from the stack of bags retained there, the portion of the bag below the slit or tearing line will tear through, separated the bag mouth from the book, but leaving the book on the bagging rack. As bags are used, the remaining books must be periodically removed and discarded, which is inconvenient.
In a second major style of central mouth tabs, termed a "tabless" style, no book portion remains on the bagging rack after use. In this style, the suspension aperture is also designed to tear through, to thereby free the mouth portion of a bag from the stack of bags on the rack. Typically, with the tabless style of bag, a portion of the bag remains attached to the mouth portion of the bag, be it a flap portion or some other extension portion. This flap or extension portion can pose a tear through problem, can become separated from the bag pack, and can sometimes look unsightly. There is accordingly an advantage in providing a cutout or cutouts through the central tab, and/or through the handles, for that matter, which leave no flaps, in lieu of utilized flapped apertures.
In order to prepare a T-shirt bag for loading with merchandise, only the first layer of the bag material of the top bag, and no other layers must be pulled forward, thereby opening just the top bag. Since the HDPE and other typical bag materials are very thin, typically between 1 to 0.5 mil thick (0.001 and 0.0005 inches), it is sometimes difficult for the checkout clerk or box person to grasp just the top layer of bag material. One can often see a sponge, or source of tacky material, such as a glue stick, retained at the top of bagging racks, with which the checkout clerk or box person can dampen his or her fingers to aid in grasping just the top layer of material of the bag. However, this takes additional time and effort in the bagging process. This cycle will have to be repeated with each successive bag to be loaded.
Several approaches have been taken to overcome the lack of a self-opening feature problem. U.S. Pat. No. RE 33,264 to Baxley et al. discloses a pack of T-shirt bags wherein spots of adhesive are placed between the rear wall of the forwardly lying bags and the front wall of the rearwardly lying bags. The use of these spots of adhesive is intended to provide for self-opening of the bags as each successive bag is pulled off the pack of bags on the bagging rack. However, the use of spots of adhesive is undesirable from a cost and reliability standpoint because an extra manufacturing step of depositing spots of adhesive on the growing stack of pillowcases as each subsequent pillowcases is stacked thereon is required. Handle flaps are formed in the bag handles which are heat sealed together in the pack of bags. These handle flaps will preferably sever from the pack of bags when the bag pack is loaded on the rack, leaving holes. In the event the flaps do not sever from the handles upon loading the pack on the rack, severing of the removed bags handle flaps will take place as each bag is removed from the bag pack on the rack.
U.S. Pat. No. 5,074,674 to Kuklies et al. discloses a packs of bags similar to that of Baxley, et al. wherein the front wall of each bag is either relieved or removed in the region of the central tab so as not to be retained by the tab receiving hook on the bagging rack, purportedly allowing the front wall of the bag to be grasped more easily to open the bag. However, this style also requires an extra, and difficult manufacturing step of removing or relieving a portion of only the front wall of each bag. The pack of bags of Kuklies et al. does not provide for self-opening of the bags.
U.S. Pat. No. 4,877,473 to Snowden et al. discloses a pack of bags wherein the tearing line has a central arched portion which forms a sub tab. This sub tab can be easily grasped and pulled forward to pull the front wall of each bag to open that particular bag. However, each subsequent bag in the pack of bags must be opened in the same manner, and thus the desired self-opening feature is absent.
U.S. Pat. No. 5,087,234 to Prader et al. discloses a method of forming a pack of easy-open T-shirt bags, wherein the bags have been corona discharge treated in the handle and bag mouth regions and such that the pressure and cutting action applied during the formation of the pack of bags will cause adjacent facing cut edges to releasably act here together until a moderate force separates them. During the step of removing a topmost bag from a pack of bags on the rack, at least a portion of the cut edge of the mouth and handle region of the front wall of the next bag will follow the bag being removed for a short distance before separating. This opens the next bag, readying it ready for loading. Prader et al. states that the pressure necessary to effect the adhesion of the treated surface is supplied during the cutting step and that any pressure involved in the formation of the handles in the bag mouth and is satisfactory for adhesion. Accordingly, by Prader et al, one would expect light frangible bonding to be formed all along the cut edges of the bag packs handle, handle apertures and central mouth tab. In contrast, Applicant has found that the frangible bonding inherently formed when corona discharge treated plastic bag packs are cut does not result in a reliable self-opening feature.
U.S. Pat. No. 5,183,158 to Boyd et al. discloses a bag pack which includes a self-opening feature, arising out plural, i.e. upper and lower, releasable means between adjacent bags. The releasable means arises out of forming compression areas through the bag stack. Boyd et al. discloses three types of suitable releasable means as including the use of low-tack pressure sensitive adhesive, the use of corona discharge treatment in combination with the application of pressure, and the application of considerable pressure through layers of adjacent bags. In Boyd, the preferred embodiment is to utilize considerable pressure through the layers of the bag pack in order to achieve a reasonable adhesion between the rear portion and front portion of each bag.
U.S. Pat. No. 5,188,235 to Pierce, et al. discloses a bag pack system with a central mounting tab on the mouth of the multiple stacked bags with a vertical perforation extending between a generally horizontal central mounting aperture and the bag mouth, to permit a bag to be removed without leaving the "book" portion of the central mounting tab on the bagging rack. In the Pierce, et al. bag pack cold pin holes are made through the handles above the handle apertures and through the central mounting tab on either side of the vertical perforation. The cold pin holes near the vertical perforation are said to provide a self-opening feature for the bags. However, in Applicant's experience, cold pin holes do not provide adequate frangible bonding necessary for a reliable self-opening feature.
Both U.S. Pat. Nos. 5,335,788 and 5,562,580 to Beasley et al. disclose self-opening polyethylene bag stacks, (composed of at least 50% by weight of high density polyethylene) and process for forming the packs, which rely on the stack of bags being formed of corona treated polyethylene film which has been compressed under high pressure in localized, upper regions under the bag mouth, and preferably spaced below the cut lines forming the bag mouth, to thus form an area of frangible bonding which is available to create the self-opening feature. The Beasley et al bags are tabbed bags, and leave a book of tabs on the bagging rack as each bag is sequentially removed from the bagging rack. U.S. Pat. No. 5,562,580 to Beasley et al. was filed as a divisional of U.S. Pat. Nos. 5,335,788 to Beasley et al., with the subject matter of U.S. Pat. Nos. 5,335,788 being directed to self-opening bag pack and with the subject matter of U.S. Pat. No. 5,562,580 being directed to a process for manufacturing a self-opening bag pack. The Beasley et al. patents stress that the conditions of heat and pressure that readily cause blocking in corona treated low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are insufficient for high density polyethylene (HDPE). The Beasley et al. patents further state that even when the cutting blades are dulled in order to increase the degree of pressure exerted on the bags during the cutting process, self-adhesion of adjacent bags for self-opening is not achieved with HDPE. In the divisional patent, the patent states, in its claim 1, that "said mouth openings defining an upper end of said bag stack". The inventors herein believe that given the narrow language of the specification, and the clear nature of the drawings, this language cannot be interpreted to broaden the meaning of "mouth" to encompass the central tab.
There are numerous bag designs which incorporate holes at top regions of the bag packs to suspend the bag on a rack. U.S. Pat. No. 2,790,591 to Rosen discloses a handleless bag having a single hole located at its top edge for suspension on a single arm of a rack, for filing with commodities.
U.S. Pat. No. 3,352,411 to Schwarzkopt discloses a bag pack with tear off portion(s) at its upper, which tear off portions can have hole, or holes formed therethrough. The tear off portions remain on the rack as each individual bag is removed from the rack.
U.S. Pat. No. 3,380,579 to Pinto discloses a handleless bag pack with a pair of holes formed in a top edge, with the pack riveted together.
U.S. Pat. No. 3,747,298 to Lieberman and U.S. Pat. No. 4,106,733 to Walitalo disclose bag dispensing units for use with handleless bags with holes adjacent a top edge of the bag packs. The holes are for use in suspending the bags on the bagging racks' arms.
U.S. Pat. No. 4,480,750 to Darcy discloses a style of handles bags wherein detachable mounting tabs are located on inside edges of the bag handles in the packs. Mounting apertures are formed in the mounting tabs, and are said to be preferably formed by a heated pin to weld the tabs together, so that as each bag is removed from the bag pack, they can be torn free from the stack of heat welded together mounting tabs which remain on the rack. The Darcy rack does not disclose a self-opening feature.
Lastly, U.S. Pat. No. 4,785,938 to Benoit, Jr. et al., discloses a bag pack with handles, where holes are formed in each handle for suspension of the handles on a rack. The Benoit, Jr. et al. bag packs employ a front-side-free bag design where the front tab is either completely from the front wall of the bag, or comparatively weakly connected thereto, while the rear tab is connected to the rear wall through a localized line of film weakening which is comparatively stronger than the front tab-front wall connection. The disclosed method of manufacturing the bag require forming individual bags first, processing the individual bags to form the front-side-free feature, and then stacking the bags and heat sealing them together.
Despite the attempts to overcome the problems associated with these presently available bags, there remains a need for an apparatus and method to manufacture, and the improved pack of T-shirt bag pack formed thereby, which (1) can be easily loaded on a bagging rack, (2) does not leave a book of plastic tabs on the bagging rack, (3) does not have flap formed in its suspension apertures, and (4) includes a reliable self-opening feature.